Subcutaneous and intramuscular delivery of liquid drugs by injection is common in the medical arts. As some medications such as insulin must be given frequently by injection to an individual, easy performance of the injections is desirable.
Many patients dislike needle injections due to pain or fear for needles. Further, blood-borne pathogens, such as HIV and hepatitis, can be transmitted to health care workers by accidental needle-sticks. Also, the disposal of used needles is a growing concern. This disposal presents a problem to individuals other than healthcare workers. Children, for example, may find used needles in the garbage, putting them at risk of contracting infection. Discarded needles likewise pose a risk to waste disposal workers.
In efforts to minimize the fears and risks associated with needle injections, several types of needle-free jet injectors have been developed. These devices penetrate the skin using a high velocity fluid jet and deliver medication into the tissue of a patient. In order to accomplish this, a force is exerted on the liquid medication. Jet injectors in general contain a fluid drug which has been transferred into a chamber having a small orifice at one end. The high velocity fluid jet can be achieved for instance by having a drive means, e.g. a ram, accelerated using either a coil spring or a compressed gas energy source. The ram impacts a plunger which in turn creates a high pressure impulse within the chamber. This pressure impulse ejects the fluid medicament through the orifice at high velocity, piercing the skin. The energy source continues to apply a force to the plunger which quickly propels the drug through the opening in the skin, emptying the syringe in a fraction of a second. The drive means may be adapted to provide a two-stage injection, which is the case for ram mechanisms, i.e. a first penetrating burst of drug at a high pressure followed by a subsequent delivery of the remaining amount of drug at a lower pressure.
During injection the nozzle should be fixed at the same point relative to the skin. If this is not the case, the jet can cause incomplete injections, so called wet shots, where none or only a fraction of the dose is delivered through the skin and the desired blood glucose regulation is jeopardised in case of insulin injection. Another consequence of poor fixation can be lacerations of the skin in case the nozzle moves laterally across the skin during injection.
Addressing this problem, U.S. Pat. Nos. 5,911,703 and 6,406,456 each disclose an injector with an integral suction compartment for pulling the skin against the tip of the injection nozzle. As disclosed, the suction compartment functions to create a seal between the skin area and the injector tip without having to compress the skin area and underlying tissue. Further, the use of a suction compartment can prevent lacerations caused by the injector tip moving relatively to the skin during an injection. WO 03/000320 discloses a jet injection device in which sealing between the nozzle aperture and the skin is secured by a nozzle having a truncated cone configuration to embed in the skin to form a hydraulic seal. In WO 05/058393 a nozzle device with an adhesive to retain the skin against the nozzle device is described, the adhesive is confined to certain areas on the device and the device may have a plurality of skin stretching members or a concave skin stretching member. The device described in U.S. Pat. No. 6,537,242 comprising a cannula also has a concave skin stretching member which can be provided with an adhesive contacting the skin to form a friction enhancing member. In U.S. Pat. No. 6,149,625 an injection aid is disclosed having an adhesive provided around the injection area to maintain the injection aid at the desired location on the skin, the adhesive surrounding the injection area in a diameter of about 5 mm. WO 98/13087 discloses a needle less injector accessory comprising a patch covered on one side with adhesive material to be put on the skin of a subject prior to injection, the injection takes place through the patch material which is pierced by the stream of injectate.
In view of the above, one of the objectives of the present invention is to provide a nozzle device which can be used in combination with a jet expelling device and which aids in providing safe and reliable jet injection of a drug. Also, a main objective of the present invention is to provide a nozzle device which decreases the frequency of incomplete injections while at the same time making it possible to limit the amount of energy required for the jet beam to penetrate the skin. Furthermore, an objective of the present invention is to provide a nozzle device which minimizes the risk of intramuscular injections. The nozzle device should be small in size, easy to use and manufactured cost-effectively.
In the alternative, it is a further objective to provide a jet injection device similar to a conventional pen type injector as regards function and configuration, in order to make the patient comfortable with the jet injection device and so that the jet injection device can easily be utilized by a non-professional user, e.g. a insulin requiring diabetic.